The present invention relates generally to a hermetic compressor assembly and, more particularly, to a direct suction compressor assembly having a crankcase mounted within a sealed housing, wherein suction gas is delivered directly to the crankcase from a suction line outside the housing by means of a suction line connector.
In general, prior art hermetic compressor assemblies comprise a hermetically sealed housing having a compressor mechanism mounted therein. The compressor mechanism may include a crankcase or a cylinder block defining a compression chamber therein in which gaseous refrigerant is compressed and subsequently discharged. Typically, and especially in the case of a compressor assembly having a pressurized housing, suction gas returning from a refrigeration system is provided to the compression chamber by means of a conduit extending from outside the housing to the compression chamber within the crankcase. This configuration is commonly referred to as a direct suction compressor assembly. In such a compressor assembly, it is known to introduce suction tubing through the housing and into a suction inlet opening in the crankcase or cylinder block that is in communication with the compression chamber. The portion of the tubing external of the housing may comprise part of a suction accumulator or may constitute a fitting to which a suction line of a refrigeration system may be attached.
In the aforementioned compressor assembly wherein a suction tube leads from an inlet opening in the crankcase through a hole in the housing, two basic problems arise. During assembly, misalignment of the crankcase with respect to the housing may cause the suction tubing to be overstressed. Specifically, manufacturing tolerances for component parts of the compressor assembly, i.e., parts having apertures and openings through which the suction tube extends, may lead to difficulty in assembling the compressor and result in unwanted stress on the suction tubing once the compressor is assembled. Stress on the suction tubing in contact with the housing produces unwanted noise during compressor operation.
A second problem associated with the above-characterized compressor assembly occurs during compressor operation, and relates to the transmission of vibration and noise from the compressor to the housing by means of the suction tubing linkage therebetween. Specifically, the compressor mechanism may undergo slight excursions in response to axial, radial, and torsional forces acting thereupon during compressor operation. Consequently, the nature of the linkage between the compressor mechanism and the stationary housing determines the extent to which vibration and noise are imparted to the housing. The suction connector must also withstand such forces and maintain integrity against leakage from the interior of the housing.
The problems discussed herein have been addressed to some extent by several prior art devices. For instance, a suction line connector is known which comprises a pair of L-fittings respectively attached to the housing and the crankcase at axially spaced locations thereon, and a connecting pipe inside the low pressure housing between the pair of L-fittings disposed axially perpendicular to and intermediate the housing and the crankcase. The connecting pipe is capable of moving relative to one or both of the L-fittings to compensate for variations in radial and axial spacing between the housing and the crankcase. A problem with such a suction tube connector is that space is required between the crankcase and the housing sidewall within the housing. Furthermore, the connector is difficult to assemble and is not suitable for a compressor having a pressurized, or high side, housing.
Another common prior art approach to compensating for radial spacing between the housing and the inlet aperture in the compressor crankcase is the provision of an 0-ring seal within the inlet opening to allow a suction tube end to variably penetrate into the aperture. Typically in this approach, an adapter at the housing aperture is welded to the housing and brazed to the tubing. A primary problem of this arrangement is that it provides for only one degree of freedom for movement of the compressor during operation.
A further prior art suction tube connector directed to compensating for spacing variations between the housing and the compressor crankcase comprises a tube entering radially inwardly from the housing sidewall and having a slotted conical flange at the end thereof to abut against the crankcase in the general area of the suction inlet aperture. The divergent end of the conical flange has a diameter greater than the suction inlet aperture, thereby permitting alignment variations.
With respect to suction line connectors for use in an indirect suction hermetically sealed compressor assembly, i.e., where the suction gas enters into the interior space of the housing, a suction line adapter device is known which is attached to the housing as by welding. This adapter comprises two pieces, one of which is welded to the housing at the location of the aperture therethrough, and the other being a coupling member attachable to a refrigeration system suction line as by brazing or the like. The coupling member with suction line attached thereto is then screwed onto the fitting welded to the housing for sealing engagement therewith. A nut threadedly engages each of the two components and brings them forcibly together at a surface to surface juncture having an 0-ring seal seated therebetween.